Synthesis of new pyrido[4,3- e ][1,2,4]triazolo-[5,1- c ][1,2,4]triazin-6(7 H )-ones
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Synthesis of new pyrido[4,3-e][1,2,4]triazolo[5,1-c][1,2,4]triazin-6(7H)-ones Mohammad N. Mawlood1, Mikhail A. Potapov1, Irina V. Ledenyova1, Oleg A. Kozaderov1, Nadezhda V. Stolpovskaya1, Khidmet S. Shikhaliev1, Andrey Yu. Potapov1* 1
Voronezh State University, 1 Universitetskaya Sq., Voronezh 394006, Russia; е-mail: [email protected]
Translated from Khimiya Geterotsiklicheskikh Soedinenii, 2020, 56(10), 1348–1352
Submitted May 3, 2020 Accepted after revision July 2, 2020
Coupling of 3-substituted 1,2,4-triazole-5-diazonium salts with ethyl acetoacetate afforded 1,2,4-triazol-5-ylhydrazones, the reaction of which with dimethylformamide dimethyl acetal leads to the formation of the corresponding readily separable 4-[2-(dimethylamino)vinyl][1,2,4]triazolo[5,1-c][1,2,4]triazine-3-carboxylates. New pyrido[4,3-e][1,2,4]triazolo[5,1-c][1,2,4]triazin-6(7H)-ones were synthesized by the condensation of the latter with primary amines. Keywords: enamine, ethyl acetoacetate, dimethylformamide dimethyl acetal, hydrazone, pyrido[4,3-e][1,2,4]triazolo[5,1-c][1,2,4]triazine, 1,2,4triazole-5-diazonium salt, [1,2,4]triazolo[5,1-c][1,2,4]triazine.
The polynucleophilic nature and the ability of 5-amino1H-1,2,4-triazole derivatives to form diazonium salts opens up access to the assembly of the [1,2,4]triazolo[5,1-c][1,2,4]triazine ring (Scheme 1). For example, the condensation of 1,2,4-triazole-5-diazonium salts with various active methylene nitriles1 yielded 4-amino-[1,2,4]triazolo[5,1-c][1,2,4]triazines that exhibit pronounced antimicrobial2 and antiviral3 activity. Similarly, intramolecular cyclization of hydrazones formed from ethyl benzimidazol-2-ylacetate and 3-substituted 1,2,4-triazole-5-diazonium salts afforded the [1,2,4]triazolo[5,1-c][1,2,4]triazin-4(1H)-one system,4 some derivatives of which are presented as effective specific inhibitors of DNA polymerases.5 Nitro derivatives of [1,2,4]triazolo[5,1-c][1,2,4]triazines obtained by condensation of 3-nitrotriazole-5-diazonium salts with nitroacetonitrile have been proposed as powerful thermostable explosives.6 [1,2,4]Triazolo[5,1-c][1,2,4]triazines synthesized by condensation of enamines or enols of heterocyclic ketones with 1,2,4-triazole-5-diazonium salts7 turned out to be promising antibacterial compounds.8 0009-3122/20/56(10)-1348©2020 Springer Science+Business Media, LLC
Scheme 1
1348
Chemistry of Heterocyclic Compounds 2020, 56(10), 1348–1352
It was shown that the products of azo coupling of 1,2,4triazole-5-diazonium salt with aromatic alcohols undergo intramolecular cyclization at the endocyclic nitrogen atom with the formation of [1,2,4]triazolo[5,1-c][1,2,4]benzo(naphtho)triazines.9 Another method that ultimately leads to the formation of the [1,2,4]triazolo[5,1-c][1,2,4]benzotriazine system was demonstrated on the basis of the condensation of a 1,2,4-triazole-5-diazonium salt with cyclohexane-1,3-diones.10 The condensation of 1,2,4-triazole-5-hydrazines obtained by reduction of 1,2,4-triazole5-diazonium salts by SnCl2 with cyclohexane-1,2-dione is an equally
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